The Imperial Festival of Science was back this year on the weekend of 7-8th of May. For the first time, the fluids CDT was there with exciting experiments to engage people of all ages. With the help of Dr Kilner and Professor Weinberg our colleagues Marco, David and Owen put together a fun and interactive stand.
The experiments included the display of fluids with different viscosities – water, glycerine and a mixture of the two – to show the phenomenon of vortex shedding.
Another fun experiment was the smoke cannon that produced smoke rings. Always fun to see mathematicians experimenting!
There was also a channel of water with mica powder where the wake behind different shapes could be observed.
Have you ever wondered why golf balls have dimples? Probably not, but either way, here’s the explanation. The dimples promote transition from a laminar to a turbulent boundary layer. You might think “that’s a terrible idea, given that it will also cause more drag.” However, turbulent boundary layers are better at mixing, which causes the fluid to be reenergised near the wall. So the separation of the flow is delayed, causing a much smaller wake behind the ball than a smooth one. Overall this results in lower drag, which allows the ball to go further. Here’s a picture illustrating this:
Anyway, I digress! Let’s go back to back to talk about the awesome experiments we were displaying. In one we could see the formation of half a ring vortex in a small paddling pool. We used tons of ink and our fingers were blue for days. My favourite quote from the audience was when a child asked Marco (with a sad face) “but what if a fish gets caught [in the vortex]? Will it die?”
All in all, this was a very fun and extremely tiring weekend. As you can imagine, repeating the same explanation over and over to a new crowd and sounding excited about it can be exhausting. But everyone was great! So congratulations to you all.
Finally I leave you with a video about the Imperial Festival, featuring your Fluids CDT!